Target trace element (TE) determines sample pre-treatment:
Avoid sample treatment when analyzing low concentration TEs (e.g. )
=> contamination or reallocation
If necessary, apply NaOCl treatment prior to measurements
=> efficient removal of the organic matrix without
=> alteration of Sr/Ca ratios and/or the carbonate structure
Mn/Ca Sr/Ca
Conclusion
13 subsamples 13 subsamples 5 6 subsamples
+ control + control
environmental parameters led to contradictory results. Proxy analyses imply that physical processes control TE incorporation in biogenic carbonates.
Incorporation of TEs into the organic matrix, however, is also controlled by
physiological processes !
One approach to improve the correlation is to chemically remove the organic matrix prior to TE measurements. We use inorganic carbonate and bivalve shell powder (Arctica islandica) to examine the effect of 12 treatments on:
?organic matter (N) content
trace element ratios (Mg/Ca, Sr/Ca, Ba/Ca, Mn/Ca)
?structure and composition of the carbonate – that is the problem
Mg/Ca Sr/Ca Ba/Ca Mn/Ca
1 2 3 4 5 6 7 8 9 10 11 12 Mg/Ca Sr/Ca Ba/Ca Mn/Ca
1 2 3 4 5 6 7 8 9 10 11 12
Method
shell powder
>> grain size
~ 30µm Inorganic carbonate
powder
Numerous attempts to correlate trace element (TE) concentrations in biogenic carbonates with
" Bleaching of biogenic carbonates – beware of changes in trace "
element concentrations!
1* 1 2 1
Krause-Nehring J , Brey T , Klügel A , and Nehrke G
1 Alfred-Wegener-Institut, Bremerhaven, 27570, Germany 2 Universität Bremen, Bremen, 28359, Germany
Rationale
What’s next
Combine spatial TE map (LA-ICP-MS, microprobe) with spatial mapping of
organic matter (Raman)
Measurements of:
?N content
=> CN Analyzer
?TE ratios
=> ICP-MS
?crystallographic structure
=> XRD
of the carbonate
Results
No treatment without side effects! The different treatments (i) vary in their efficiency to remove organic matter, (ii) cause treatment and element specific changes in trace element ratios, and (iii) can even alter the structure and composition of the carbonate.
Treatment 1 to 12 + control
A. islandica shell
>> one valve
13 subsamples
Treatment 1 to 5 + control
0 No treatment (control) 1 Washing only
2 Acetone 3 H2O2
4 NaOH 5 NaOCl 6 Mucasol
7 Acetone+H2O2+Acetone 8 Acetone+NaOH+Acetone 9 Acetone+NaOCl+Acetone 10 Acetone+Mucasol+Acetone 11 Acetone+H2O2+NaOH+
Acetone
12 Acetone+H2O2+NaOH+
NaOCl+Mucasol+Acetone
sample treatment causes changes of TE/Ca ratios AND
NaOH treatment alters the crystallographic structure of the carbonate
Inorganic carbonate powder
A. islandica shell powder
Mg/Ca Sr/Ca Ba/Ca Mn/Ca % calcite other constituents after sample treatment
1 100
2 100
3 100
4 0 Ca(OH)2 , Na2CO3 , Na2Ca(CO3) 2*5H2O , NaOH
5 75 NaCl
most efficient N removers:
=> NaOCl (# 5,9,12)
=> NaOH (# 4,8,11,12) BUT
: NaOH treatment
=> significant decrease :
=> no clear pattern
=> tendency to increase Sr/Ca
Mg/Ca, Ba/Ca, Mn/Ca
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
no significance increase
decrease
N content (µg / mg) - after sample treatment N content (µg / mg) - untreated sample
1 - 12 treatment number (see Methods)
A. islandica shell cross-section of the shell umbo with LA-ICP-MS tracks
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